Cytokinins or CKs are a group of chemicals that influence cell division and shoot formation. They were called kinins in the past when the first cytokinins were isolated from yeast cells. They also help delay senescence of tissues, are responsible for mediating auxin transport throughout the plant, and affect internodal length and leaf growth. Cytokinins and auxins often work together, and the ratios of these two groups of plant hormones affect most major growth periods during a plant's lifetime. Cytokinins counter the apical dominance induced by auxins; they in conjunction with ethylene promote abscission of leaves, flower parts, and fruits.  The correlation of auxins and cytokinins in the plants is a constant (A/C = const.). [ citation needed ]
In the absence of GA, many DELLAs are present to repress GA responses, but the formation of the GA-GID1-DELLA complex increases the degradation of DELLAs.  The SCF complex is composed of SKP1, CULLIN, and F-BOX proteins.  F-box proteins catalyze the formation of polyubiquitin on target proteins to be degraded by the 26S proteasome.  The formation of the GA-GID1-DELLA complex is believed to cause a conformational change in DELLA, which enhances recognition of DELLAs by F-box proteins.  Next, the SCF complex promotes ubiquitylation of DELLAs, which are then degraded by the 26S proteasome.  Degradation of DELLAs allows GA regulated growth to resume. Thus, GA stimulates growth by activating the degradation of DELLAs.